Photoluminescent sensors or probes are a widely employed method of measuring analyte concentration, typically oxygen, within an enclosed space such as a package or container. See, for example United States Published Patent Applications 2009/0029402, 2008/8242870, 2008/215254, 2008/199360, 2008/190172, 2008/148817, 2008/146460, 2008/117418, 2008/0051646, and 2006/0002822, and U.S. Pat. Nos. 7,569,395, 7,534,615, 7,368,153, 7,138,270, 6,689,438, 5,718,842, 4,810,655, and 4,476,870.
Briefly, analyte concentration within a package or container can be measured by placing an analyte sensitive photoluminescent probe within the package or container, allowing the probe to equilibrate within the package or container, exciting the probe with radiant energy, and measuring the extent to which radiant energy emitted by the excited probe is quenched by the presence of the target analyte. Such optical sensors are available from a number of suppliers, including Presence Precision Sensing, GmbH of Regensburg, Germany, Oxysense of Dallas, Tex., United States, and Luxcel Biosciences, Ltd of Cork, Ireland.
Such probes can be used to quantify a rate of oxygen uptake by biological and chemical samples, thereby serving as a biomarker of cell or organism viability. Also, many oxygen-dependent enzymatic and chemical reactions can be monitored via oxygen consumption, providing a means for evaluating the performance of various reactants, catalysts, enzymes, etc. and the effect of various conditions (e.g., temperature, pressure, concentrations, etc.).
The placement of photoluminescent probes into vials for monitoring oxygen consumption by a sample placed into the vial is known. U.S. Pat. Nos. 5,371,016 and 6,080,574 describe optical systems for measuring sample sterility and microbial growth by monitoring oxygen consumption by a sample placed within a vial having a fluorescence-based oxygen sensor built into the vial. W098/15645 describes an optical system that uses a solid-state luminescence-based oxygen sensor to assess a biological sample containing living micro-organisms by measuring gradients of dissolved oxygen within the sample. U.S. Pat. No. 5,882,922 describes a system for measuring oxygen consumption in samples using wells containing a solid-state oxygen sensor coating applied to the bottom of each well or soluble oxygen probes added to each sample.
While effective for accurately quantifying a rate of change in analyte concentration within a sample (e.g., oxygen uptake by biological and chemical samples) and thereby allowing quantification of viable microbes within a sample or quantification of a chemical reaction, the systems and techniques employing such technology are time consuming, often creating a choke-point in the distribution of products, such as foodstuffs, from a production facility into the stream of commerce.
Accordingly, a substantial need exists for quick, simple and inexpensive technique for hastening quantification of viable microbes within a sample or quantification of a chemical reaction employing photoluminescent probes that does not sacrifice accuracy or reliability.